The aim of this research is to understand the nature of the response of chick embryo cells to growth stimulating agents. We have identified a large array of unrelated metabolic responses, including the differentiated functions of the cell. The most reliable and rapid of the cell responses is increased uptake and metabolism of glucose. Our experiments are designed to identify the structural and metabolic basis for this early change. We also wish to know how metabolism, differentiated function and growth are coordinated with one another, as they appear to be. This has raised questions about the nature of the cell cycle in growth-inhibited and growth-stimulated cultures. Our experiments should tell us whether the conventionally accepted view of the GO state for so-called resting cells has any validity.